It's a great one, but I wouldn't say the best. Some of my favorites are "Lord of the Underworld," "Scorched Feathers," and "Viridi, Goddess of Nature."
EDIT: I changed my mind; Lightning Battle is one of the best.
I've had two songs stuck in my head for days.
Correction: I've had two awesome songs stuck in my head for days.
http://www.youtube.com/watch?v=gaLPpKCC9pg
http://www.youtube.com/watch?v=GDflVhOpS4E
I'm a huge fan of metal: progressive metal, power metal... a cappella metal?
http://www.youtube.com/watch?v=fsVlfuWCRpw
Edit/Note: Sometimes I think songs are misunderstood. Some people would consider this song demonic, but it's not at all. I mean, really? It's just from a darker perspective.